Have ever seen one of the old triangle table shiners, the kind that fits between the triangle space made between two chip stacks together. They were made so you could close them flat for hiding and open them up for use at a 45 angle.
At any rate it occurs to me that one could make something of a similar nature from a key chain locket. Where the photo normally would go one puts instead a mirror. These for example are lockets:
http://www.bimmerzone.com/prodbmwkey.htm
What I mean is it would look innocent enough closed with a car key attached just placed behind the chips and when required presto changeo up pops the mirror.